Is it possible to crease a NURBS vertex?
In your example a bezier curve will make it easier to get 'sharp' points in your curve as the control handles for each point give more control over how the curve enters and leaves each point.

If you do need to use nurbs and also need a 'sharp' point you can place three points close together which reduces the smooth interpolation between points to what visually appears to be a point.



In edit mode if you zoom right in you can see -